Electrical system



April 15 1924.

' H. D. JAMES ELECTRICAL SYSTEM Filed Oct. 18. 1919 INVENTOR 79 dzmm WITN SES:

ATi'ORNEY Patented A... 15, 1924. p

UNITEDISTATES ATE T OFFICE.

Y D. IA, 01' EJGIWOOD PARK, PENNSYLVANIA: ASSIGNOB TO WESTING- HOUSE me & nmaonmmo mm, A. CORPORATION 01" PENNSYL- VAIIA.

mach: SYS'IEI.

Application fled October 18', 1819. Serial No. 881,548.

To all whom it may concern" Be a known um 'I Hnimr 1). JAMES,

a citizen of the United States, and a resident of Edgewood Parks in the county of Allegheny and State of vrennsylvaniay have invented a new and useful Improvement in Electrical Systems, of which the following is a specification. 3

' My invention relates to control systems for dynamo-electric machines and particularly to systems for controllin the direction of operation and the spec of electric motors by varyin the polarity and excitation of a separate y excited generator.

One object of my invention is to provide a system of motor control wherein the field excitation of the motor must reach a predetermined value before the excitation of the generator field can be altered.

A further object of my invention is to provide a system of control in which the inductive lag of the motor-field-winding will be overcome and the motor field current will reach its full value before the generator field current can be changed.

My invention finds special application in connection with motor-generator sets, the armatures of which are connected in seriescircuit relation and the fieldanagnet windings of which are separately excited. In systems of this type, the speed of the motor is first increased to the full value obtainable by increasing the generator volts. e. Further acceleration is then obtained by msorting resistance in the circuit of the motorfield-magnet winding. It is essential that I this sequence of control be maintained during acceleration and that the corresponding sequence be maintained, in the reverse order, during deceleration.

According to my invention, a motor-genorator set is provided with separately ex cited field-magnet windings, and. adjustable rheostats are inserted in the field-magnet winding of each machine. The circuit of the field-magnet'winding of the dynamoelectric machine, acting as a motor in this on comprises a relay that is adapted to he: closed when the motor field current reaches a maximum value. This relay controls a pilot motor, or other operating mechanism for v the resistance in the cirmg cuit oi the fiel -magnet winding of the gen orator.

The single figure of the accompanying drawing is a diagrammatic view of the main and control circuits for a pair of dynamoelectric machines embodying my invention. The figure of the accompanying drawing shows a generator armature 1 that is connected in closed circuit with a motor armature 2. The generator armature is driven by a prime mover 3 that is here illustrated as an induction motor but which may be any form of engine suitable for driving the generator. Separately excited fieldmagnet windings 4 and 5 and their corresponding field rheostats 6 and 'F are respec tively rovided for armatures 1 and 2.

a A pi ot motor 8 is'provided for operating the rheostat 6 and is controlled by push buttons 9 that are respectively designated Fast and Slowf A current relay 10 has an actuating coil in series with the field magnet Windin 5 and is accordingly actuated in accordance with the value of current flowing through the field-magnet Winding 5 to partially complete the circuit for the pilot motor. under predetermined condi--' tions to be hereinafter-set forth.

The rheostat 6 may be of any type adapt ed to vary and reverse the current flowing through the field'magnet winding 4-. The

rheostat here shown is provided with contasting arms 11 that are adapted to be actuated by the pilot motor 8 to insert vary ing degrees of resistance in the circuit of the field-magnet winding 4;.

The rheostat i in the circuit of the fieldmagnet winding 5, may be controlled in any suitable manner. It is here shown in the form of the usual fieldcircuit resistor in which the position of the arm 12 determines the resistance in the circuit of the motor-field winding.

The current relay i0 is adapted. to be actuated to its closed position when the motorfield current reaches substantiallyits maximum value. This condition obtains when the resistance of the rheostat 7 is substantially out out. Under normal conditions.

the relay l0 interrupts the circuit for the pilot motor 8. It completes this circuit only when substantially a. maximum value ofltd ing to the direction in which it is desired to operate the motor 8.

The motor is started from rest and accelerated by applying full field excitation to the motor and by gradually increasing the voltage applied across the motor armature; The motor field current is brought to a maximum value by moving the arm 12 to such position as to completely shunt the rheostat 7. As soon as the motor field strength builds to its maximum value, the value of the current in the field circuit is such that the relay 10 is actuated to its closed position to partially complete the circuit of the pilot motor 8. It should be pointed out that, unless substantially a maximum field current traverses the winding 5, the relay 10 will not be actuated and, therefore, further acceleration in the motor speed cannot be obtained until the inductive lag of the motor field-magnet winding is overcome and the motor field current attains substantially its maximum value. In view of the fact that the motor field excitation is substantially coincident with the flow of exciting current, the motor field-exciting current will attain its maximum value as soon as the inductive lag of the motor fieldmagnet winding is overcome. After the current relay 10 has been closed, thereby partially completing the circuit for pilot motor 8, it will remain in this position until further alteration of the motor excitation.

Further acceleration of the motor from this point is obtained by depressing push button 9 marked Fast, by means of which a circuit is completed through the motor armature 8 and the relay 10 to the exciter circuit. The motor 8, when energized in the above indicated manner, rotates rheostat arms 11 in a direction to remove resistance from the. generator field winding circuit and,

therefore, to increase the voltage applied to the motor armature 2.

When the generator field winding reaches substantially maximum excitation, the voltage impresed, across the motor armature is at its maximum value and further increase of motor specdis obtained by adjustments of the motor field rheostat 7. When the rheostat arm 12 is moved from its short-circniting position, the relay 1'0 interrupts the circuit for pilot motor 8, and further change in the generator excitation is prevented until the field excitation of the motor is again brought to maximum degree.

If it is desired to decelerate the motor, the procedure described for accelerating the motor must be followed in the reverse order. In other words, the motor field must first be brought to a maximum value before the generator field can be altered. The enerator field excitation is then decrease by depressing the push-button switch designated slow to effect adjustment of the motor field excitation is at substantially its maximum value.

The direction of operation of the motor may be reversed by operating the rheostat 6 to reverse the direction of the generator excitation. Further changes in the motor speed are then obtained in the manner hereinbefore described.

It will be apparent that my invention is capable of applications other than those herein described, and I desire, therefore, that only such limitations shall be imposed as are set forth in the appended claims.

I claim as my invention 1. A control circuit comprising a pair of separately excited dynamo-electric machines, means for respectively changing the excitation of said machines and a currentresponsive relay for delaying-the action of the means corresponding to one of said machines until the excitation of the other of said machines reaches a predetermined degree during acceleration and deceleration.

2. A control system comprising a motor, means for varyin the excitation thereof, a generator supplying energy to said motor, poweroperated means for varying the excitation of said generator, and a single means dependent upon the degree of saturation of said motor for delaying the changw in the excitation of said generator during acceleration and deceleration.

A motor-control system comprising a separately excited motor, a separately excited generator supplying the armature of said motor, means for varying and reversing the electromotive force of said generator, and a single relay for delaying the action of said voltage-controllin means during acceleration and deceleration until said motorfield excitation reaches a predetermined value.

4. A motor-control system comprising it separately excited motor, means for varying the field strength thereof, a separately excited generator exclusively supplying energy to said motor, an electroresponsive evice for controlling the electromotive force of said generator, and a single current-responsive relay for delaying the action of said device during acceleration and deceleration until the field strength of said motor exceeds a predetermined value.

5. A control system comprising a pair of separately excited dynamo-electric machines, means for varying the excitation of said means comprising a pilot-motor for varying motor and sand; generator, and-a single and reversing the excitation of one of Sci means responsive only to the full field curmachines, means for varying the excitation rent of said motor for permitting changes 5 of the other machine, and means, dependent in the excitation of said generator. upon the field-winding conditions of the In testimony whereof, I have hereunto other of said machines, for delaying the subscribed my name this 8th day of Oct. action of said pilot-motor. I 1919.

6. A control system comprising a motor, 10 a generator for supplying energy thereto, HENRY D. JAIIES. 

